For example, in the mining industry hydraulic machines are used which do not have any internal unit for generating a pressure in a hydraulic fluid, typically hydraulic oil. One example of such hydraulic machines are rock drilling machines. These hydraulic machines thus, constitute users of an oil flow, which for example may have to amount to up to 40 liters/minute and have a pressure of 120 Bar. Thus, separate hydraulic units are used for providing the hydraulic machines with a pressurized oil flow.
A hydraulic unit comprises a motor which drives a hydraulic pump for generating a pressurized oil flow, an oil tank, and a heat exchanger for cooling of oil as it flows back from the user to the oil tank. It is desirable that a hydraulic unit for use in the mining industry is compact and manually movable in narrow mine galleries to be placed about 10-30 m behind a user. Also in other technical areas where hydraulic machines are used in tight spaces, use is found for such compact manually movable hydraulic units, one such example is percussive breaking machines, which are used for excavation in buildings. For example, the hydraulic unit called ATLAS COPCO HYDRAULIC POWER PACK LP 18-40 may be mentioned, which weighs about 130 kg and has the dimensions 815×605×690 mm, and which has a frame which is provided with a pair of wheels. ATLAS COPCO HYDRAULIC POWER PACK LP 18-40 comprises an air-cooled heat exchanger which is equipped with a fan and an electric motor in the form of an asynchronous motor.
There is a need for more compact separate hydraulic units, inter alia within the mining industry and on building sites.